The Science of Religious and Philosophical Exemptions Saad B. Omer, MBBS MPH PhD Departments of Global Health, Epidemiology, and Pediatrics Emory University, Schools of Public Health & Medicine & Emory Vaccine Center

Vaccine Coverage Levels – United States 1962-2007 Combined 4-3-1: Four or more doses of DTP/DTaP/DT, three or more doses of poliovirus vaccine, and one or more doses of any measles-containing vaccine. Combined 4-3-1-3: Four or more doses of DTP/DTaP/DT, three or more doses of poliovirus vaccine, one or more doses of any measles-containing vaccine, and three or more doses of Haemophilus influenzae type b vaccine. Data prior to 1993 were collected by the National Health Interview Survey and represent 2-year-old children. Data from 1993 are from the National Immunization Survey and represent 19-35 month-old children. Different methods were used for the two surveys. MMWR 2008;57(35);961-66 CDC Pink Book; 2009

Evolution of Immunization Program and Prominence of Vaccine Safety Chen & Hibbs, Pediatr Ann. , 1998

School Immunization Requirements State laws (not federal) Major role in low rates of vaccine preventable diseases Exemptions Medical Religious Personal belief (philosophical) exemptions

Exemptions to School Immunization Laws TYPE OF EXEMPTION(S) ALLOWED Religious & Medical (28) Medical only (2) Philosophic, Religious & Medical (21) updated March 2005 www.vaccinesafety.edu

Relative Risk of Measles and Pertussis in Exemptors from School Laws Measles Pertussis CO (1987-98) 22 5.9 U.S. (1985-1992) 35 Feikin et al. JAMA. 2000; Salmon et al, JAMA. 1999.

Complexity of Administrative Procedures to Obtain Exemptions & Proportion of Children with Exemptions Source: Rota et al., AJPH, 2001

State Policies Easy process = High exemption rates Exemption rates associated with individual risk of pertussis & measles State policies Disease incidence?

Associations between State Exemption Policies and Pertussis Incidence, 1986-2004 Unadjusted IRR (95% CI) Adjusted IRR Type of exemption Only Religious Exemption Reference Personal Belief Exemption 2.06 (1.77-2.40) 1.48 (1.03-2.13) Exemption ease Difficult Medium 1.27 (1.06-1.51) 1.35 (0.96-1.91) Easy 1.90 (1.60-2.28) 1.53 (1.10-2.14) Adjusting for allowing parental signature for school immunization forms, proportion inside urbanized area, income (11 categories), and education (7 categories) Omer et al., JAMA, 2006

Non-Medical Exemptions by year 1991 - 2003

Nonmedical Exemptions for States With Religious Exemptions and With Personal Belief Exemptions -1991 - 2004 Only Religious Exemptions Permitted Personal Belief Exemptions Permitted Exemption Rate Omer et al., JAMA, 2006 Data updated

Nonmedical Exemptions by Ease of Exemption 1991 - 2007 Easy Exemption Policy Medium Exemption Policy Difficult Exemption Policy Omer et al., JAMA, 2006 Data updated

WA State Counties’ School Entry Exemption Rates 2006-2007 Omer et al., New Eng Journal of Medicine, 2009

Cluster Search The idea is to divide the plane into zones such that the probability of having an event of interest is the highest inside the zone, compared to outside the zone. The radius of these windows varies from zero to an upper limit that can be specified -----------------------------

P-value Source: Assunção & Kulldorff

Location of Space-time Pertussis Clusters and Distribution of Schools Inside & Outside Spatial Exemptions Clusters Omer , Enger, Moulton et al., Am. J. Epi., 2008

Relative Locations of Pertussis Space-time Clusters & Exemptions Spatial Clusters Unadjusted OR 3.0 (2.5 – 3.6) Adjusted OR 2.7 (2.2 – 3.3) Overlap of Exemptions Clusters with Pertussis Clusters Omer , Enger, Moulton et al., Am. J. Epi., 2008

Locations of Schools Included in Exemption Clusters in California and Massachusetts

Incidence Rate Ratios (95% CI) Incidence Rate Ratios (IRR) of Pertussis in Census Tracts Inside vs. Outside Exemptions Clusters   Incidence Rate Ratios (95% CI) California Massachusetts (n=3950) (n=7891) All ages 1.25 (1.09-1.44) 1.21 (1.04-1.41) Age-group 0-4 yrs 0.95 (0.81-1.12) 5-17 yrs 2.0 (1.60-2.50) 18 yrs or older 1.31 (1.07-1.61) Bold: p<0.05

Course of a Measles Outbreak by Exemption Status Mesa County, Colorado; 1994-1995 Feikin et al., JAMA, 2000

MMWR, 2008

MMWR, 2008

Parents’ Perceptions by Child's Vaccination Status Salmon , Moulton, Omer et al., AJPH, 2005

Characteristics of Unvaccinated (“Zero Dose”) vs Characteristics of Unvaccinated (“Zero Dose”) vs. Under-vaccinated Children Unvaccinated children more likely to be: Male White Belong to households with higher income Married mother with a college education Live with ≥ 4 children Smith, Chu , & Baker, Pediatrics, 2004

Trust in Sources of Vaccine Information HCP: Health Care Provider VIS: vaccine information statements CAM: Complementary & alternative care provider DTP: Dissatisfied parents together Salmon, Moulton, Omer et al. Arch Ped Adol Med, 2005

Disease Susceptibility and Severity and Vaccine Safety and Efficacy Health Care Provides in High Category Association with Parent Responses Exempt Vaccinated Odds Ratio Disease Susceptibility 11.3 5.7 1.34 Disease Severity 30.2 29.4 1.36 Vaccine Efficacy 87.0 88.8 1.21 Vaccine Safety 88.9 93.9 3.28* Were none of thesse statstically significant? * P Value <0.05 Salmon , Pan, Omer et al., Human Vacc. 2009

States with Permanent Only, Temporary Only, and Permanent & Temporary Medical Exemptions –2004-2008 Incidence Rate Ratios of Medical Exemptions by Type of Exemption Permitted Temporary Only Reference Perm. & Temp. 2.17 (0.77, 6.12) Permanent Only 4.07 (1.17, 14.19)

Vaccine Delay Novel vaccine schedules Consequences not studied in detail Risk of vaccine preventable diseases is not constant across childhood Vaccine delays may leave young children vulnerable Potential exacerbation of health inequities involve spreading vaccines Omer et al., New Eng Journal of Medicine, 2009 Offit & Moser, Pediatrics, 2009

Conclusions Effective administrative controls Ease of filing paperwork vs. vaccination Identification of high-risk geographical areas Impact of actions of exemptors on overall risk Engage local stake-holders Importance of providers Should states report a clustering statistic? These findings highlight the impact of state-level policies on pertussis incidence and support the need for effective administrative controls over granting non-medical exemptions. State-level policies on non-medical exemptions and administering immunization requirements should be viewed as part of the efforts to control pertussis and maintain a low incidence of other vaccine preventable diseases.

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